Materials are for both 2D and 3D. In 2D the default material supports tinting tho. Behind the scenes, the Sprite Renderer sends its tint color to the shader to affect the final output colors. You could use a different shader/material to alter how that that tint color is interpreted and displayed. Shader Graph 2023 + supports this now.
Overall, sprite colors can be influenced by:
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scene lighting, global lights & other lights (if you’re using 2D Renderer, you need to look for Light2D)
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color tinting (see Sprite Renderer’s color property, darkening or alpha?)
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something going on with the shader or material (do you have the right lit/unlit material?)
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the colors they’re adjacent to (purely a perceptive difference)